Several recent initiatives are aimed at deploying “massive” constellations of satellites. Massive is intended to mean the fact that they comprise more than 100 satellites. Such is the case for example for two public initiatives with the objective of deployment by the year 2020: OneWeb and SpaceX.
However, the approach of telecom technology in respect of these solutions remains very close to known technologies. It relies in particular on producing satellite spots, each of the spots being served by one of the beams of a particular satellite.
This approach does not actually exploit the massive aspect of the constellation: at a given instant, a receiver has a link with just one satellite, whilst several satellites are generally visible. The link budget is therefore dimensioned within the context of this single link.
In respect of dimensioning constraints on the antennas relating to the desired size of the satellite spots, this approach is rather more oriented towards constellations in low terrestrial orbit (also known as Low Earth Orbit, or LEO). However, the use of LEO satellites leads to greater Doppler effects, shorter visibilities, and therefore more inter-cell transfers (also known as handover). LEO satellites have a less extensive coverage than satellites in higher orbit, and therefore require Inter-Satellite Links (ISLs), and/or more satellite gateways on the ground.
The dimension of the spots cannot be reduced as much as desired because of the bulkiness of the antenna on the satellites. This therefore also generates the necessity to manage residual multiple access, thereby causing a reduction in availability for the user.
Finally, the implementation of satellite spots impacts the design of the satellite, and in particular the design of its antenna. It therefore requires high intelligence in managing the networking.